Ophelie David of France took bronze.
On the men's side, Jean Frederic Chapuis surprisingly won the men's ski cross title, beating fellow Frenchman Bastien Midol in the final for his first major victory.
John Teller of the United States took bronze while the fourth finalist, Jouni Pellinen of Finland, fell and failed to finish.
Chapuis has never won a World Cup event, with a third-place finish in Germany last year his best finish.
In the women's race, 20-year-old Smith needed a strong comeback in the semifinals, when she was in last position but managed to finish second to reach the final.